Tablets and capsules are the most common dosage forms for the oral administration of nutritional, medicinal, or other therapeutic products. It is well-known, however, that these dosage forms are unacceptable for use by people who have difficulty in swallowing tablets and capsules and that the difficulty is exacerbated by larger tablets and capsules and, in some instances, by the bad taste of the medication. It is generally accepted that these types of problems with medications are serious because they may lead to a failure on the part of patients to comply with the medication regimen ordered by the physician.
The common alternatives to conventional tablets and capsules are chewable tablets and aqueous or hydroalcoholic liquids such as syrups, suspensions and elixirs. Such dosage forms are commonly used for antacids, analgesics, cough and cold medications, antibiotics, vitamins and many other nutritional or medicinal products. In general, these forms do not significantly improve the taste of a medication or make it easier to swallow larger doses. For example, antacids in either chewable tablet or aqueous suspension form are generally disliked because they are gritty, astringent and leave an unpleasant aftertaste.
Although aerosol packaging has found high consumer acceptance in many areas, including pharmaceutical products such as inhalants, it has not heretofore been considered for use in formulations requiring a high concentration of suspended solids, i.e., greater than 5 to 13%, because a high solids content usually causes malfunctioning of the aerosol valve. It is neither economical nor practical to dispense therapeutic agents in the very dilute formulations which would be required for dispensing through an aerosol valve. Moreover, such dilute formulations usually produce an uncontrollable and unmeasurable spray, thereby making it difficult to control or measure the amount of the formulation being dispensed. A further difficulty with aerosol packaging is that most aqueous aerosol solutions would be unacceptable for dispensing medications because the dissolution of the active ingredient prior to ingestion could reduce its bioavailability and also produce an unpleasant taste.
There are several prior art patents which disclose anhydrous aerosol foams. For example, U.S. Pat. No. 3,770,648 discloses an anhydrous aerosol foam composition for external use which incorporates a silicone resin in a solution of organic solvents to produce a stable "quick breaking" foam when the foam is rubbed into or spread over a surface on which it has been deposited. The '648 patent does not disclose any anhydrous foam products which are suitable for ingestion. It also does not teach any type of dosable or meterable foam for dispensing high concentrations of solid therapeutic agents.
U.S. Pat. No. 3,849,580 discloses an aerosol dispensing system which delivers non-aqueous butter-like edible fat compositions in a foam form. These foams contain no foaming agent and are intended to be used as food spreads.
U.S. Pat. No. 4,425,164 teaches the preparation of an aerosol spray cookware lubricant composition similar to the product which is commercially available in food stores under the trademark "PAM". This spray is formed from a mixture of a vegetable oil solution of an emulsifier (lecithin) in admixture with at least 10%, preferably 20 to 30%, of a hydrocarbon propellant and up to 15%, preferably 3 to 10%, of suspended flour or starch particles. The resulting product is a spray in which the particles serve as a visual indicator that the spray is being uniformly applied to the cooking surface. There is no disclosure or suggestion of a directly ingestible stable foam product capable of yielding repeatable, measurable doses of an active, solid therapeutic agent from an aerosol container.
Other disclosures of vegetable oil, lecithin-containing edible aerosols (U.S. Pat. No. 4,188,412 and 3,821,007) also indicate that such materials are sprays rather than foams. These patents additionally teach that foaming action would be undesirable in such a product.